A Paschal Blue Moon Coming March 31

This may sound like a repeat but the full Moon that shows up for a second time this month (March 31st at 8:37 a.m. EDT) is known as a “Blue Moon.” But what you may not know is that this full Blue Moon is also known as the “Paschal Blue Moon” and it has a special connection to Easter.

How The Moon Shapes The Date of Easter

According to religious rules, the first Sunday after the Paschal Moon is usually designated as Easter Sunday, as will indeed be the case this year (Easter falls on April 1st).

However, the church date assumed for the full Moon does not always coincide precisely with the astronomical one. For example, Easter, in practice, is determined from other formulae such as Epochs and Golden Numbers. These rules also state that the vernal equinox is fixed on March 21, even though at European longitudes from 2008 through 2101 the equinox will occur no later than March 20. In 2038 Easter will be observed as late as it can possibly come, on April 25. The earliest date for Easter is March 22, which will not happen until 2285.

Fun Fact: We can only have a Paschal “Blue” Moon in March.

(Continued Below)

When Was The Last Paschal Blue Moon?

The last time we had one was in 1999 (19 years ago — remember the Metonic Cycle?). In that year, that second March full Moon fell on a Wednesday, so Easter Sunday fell on April 4th.

If you’re wondering when the last time Easter Sunday fell on April 1st, that was in 1956.

But when did we have a case similar to this year — a Paschal Blue Moon on March 31st, followed the very next day by Easter Sunday? In 1714, the full Moon was on March 31st at 3:17 Universal Time, followed the next day by Easter Sunday. But that was valid only for Europe and the Eastern Hemisphere. For the “New World” (North America) the full Moon occurred the day before (on March 30th).

We must go back to the year 1646 to have a case similar to this month: A Paschal Blue Moon on Saturday, March 31st, was followed by Easter Sunday the very next day.

And finally, our next Blue Moon will be on October 31st (Halloween) in the year 2020.

Joe Rao is an astronomer and contributes regularly to the Farmers' Almanac.

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However, the Eastern Orthodox church determines Easter a different way, so that it is either a week or several weeks later than Western Easter.
Just wanted to say that this article is not about universal determination of Easter Sunday.

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